Racing centrifugal clutch assembly

ABSTRACT

In a centrifugal clutch including a drive shaft, a pair of pulley flanges mounted on said drive shaft and providing therebetween a groove for a V-belt, one of the pulley flanges being axially movable on the drive shaft to vary the radial position of the V-belt with respect to the pulley flanges, apparatus for axially moving said movable pulley flange in response to the angular velocity of the drive shaft, comprising a cam ramp fixedly mounted to said drive shaft in spaced relationship with the side of the movable pulley flange, said cam ramp including a portion curved toward said movable pulley flange, a centrifugal weight mounted for radial movement with respect to said movable pulley flange and said cam ramp, and means for inhibiting the radial movement of said centrifugal weight until a predetermined drive shaft angular velocity is reached.

United States Patent Schupan 1 51 Aug. 22, 1972 [54] RACING CENTRIFUGALCLUTCH ASSEMBLY [72] Inventor: Fred A. Schupan, York, Pa.

[73] Assignee: AMF Incorporated [22] Filed: Aug. 26, 1970 [21] Appl.No.: 67,147

Primary Examiner-C. I. Husar Attorney--George W. Price and Barry H.Fishkin [57] ABSTRACT In a centrifugal clutch including a drive shaft, apair of pulley flanges mounted on said drive shaft and providingtherebetween a groove for a V-belt, one of the pulley flanges beingaxially movable on the drive shaft to vary the radial position of theV-belt with respect to the pulley flanges, apparatus for axially movingsaid movable pulley flange in response to the angular velocity of thedrive shaft, comprising a cam ramp fix edly mounted to said drive shaftin spaced relationship with the side of the movable pulley flange, saidcam ramp including a portion curved toward said movable pulley flange, acentrifugal weight mounted for radial movement with respect to saidmovable pulley flange and said cam ramp, and means for inhibiting theradial movement of said centrifugal weight until a predetermined driveshaft angular velocity is reached.

7 Claims, 6 Drawing Figures PATENTEmuczz m2 FRE A.

PATENTEDwczz m2 SHEET 2 OF 3 INVENTOR FRED A. SCHUPAN ATTORNEYP'A'TENTE'Dwszz m2 FIG. 3

FIG. 4

FIG.6

FIG.5

INVENTOR FRED A. SCHUPAN BY ATTORNFY RACING CENTRIFUGAL CLUTCH ASSEMBLYBACKGROUND This invention relates to variable speed V-belt transmissionsby which power is transmitted from a driving shaft to a driven shaft andmore particularly to an improved centrifugal clutch for such variablespeed transmissions. Transmissions of this type are commonly utilized insmall vehicles, such as snowmobiles, golf carts, motorcycles and thelike.

In transmissions of this type each of the shafts commonly carries apulley including a pair of opposed pulley flanges which between themprovide a V-shaped groove adapted to receive a belt connecting the twopulleys. The V-belt is normally mounted at the bottom of the pulley onthe driving shaft and the top of the pulley on the driven shaft. Oneflange of each of the pulleys is movable against a bias. The pulley onthe driving shaft is operatively connected to means having centrifugalweights for shifting the movable pulley flange in response to enginespeeds and is called a centrifugal clutch. With increasing drive shaftspeed the centrifugal clutch will close the space between the pulleyflanges and urge the V-belt outwardly. This will pull the belt inwardlyin the pulley on the driving shaft thus moving the transmission from ahigh torque to a high speed mode.

In applications where this type of transmission is utilized,particularly snowmobiles, the sensitivity of the drive with respect tothe throttle is of the utmost importance. The operator of the vehicleshould have a sensitive control wherein the speed of the vehicle can besmoothly accelerated and decelerated to provide the needed control ofthe vehicle for the uneven terrain that these vehicles often are drivenacross. In the past such vehicle speed control has been lacking due to apredilection for the centrifugal weights in the clutch to stick and beresponsive only to large increase in engine speed, causing lurching andlunging of the vehicle.

In racing applications it is desireable to have a lunge at the start ofthe race to get the vehicle quickly up to maximum speed. In thissituation, it is desireable to have the centrifugal weights in theclutch maintained in a non-driving position until the engine speed hasbeen increased to a predetermined point, whereupon the weights lurchoutwardly, accelerating the vehicle at a rapid rate.

SUMMARY It is, therefore, an object of this invention to provide animproved variable speed drive for small vehicles.

It is a further object of this invention to provide a centrifugal clutchfor a variable speed transmission having increased responsiveness toengine speed.

It is a further object of this invention to provide an improved variablespeed drive adaptable for racing applications.

It is a still further object of this invention to provide a centrifugalclutch having improved centrifugal weight assemblies and also adaptablefor high engine speed engagement for racing applications.

In accordance with these and other objects, apparatus according to theinvention may comprise in combination with a drive shaft, a pair ofpulley flanges mounted on said drive shaft and providing therebetween agroove for a V-belt, one of the pulley flanges being axially movable onthe drive shaft to vary the radial position of the V-belt with respectto the pulley flanges, means for axially moving said pulley flanges inresponse to the angular velocity of the drive shaft, including: a camramp fixedly mounted to said drive shaft in spaced relationship with theside of the movable pulley flange away from the other pulley flange,saidcam ramp including a portion curved toward said movable pulleyflange, a weight mounted for rolling movement between said cam ramp andsaid movable pulley flange and means for precluding the rolling of saidweights until the drive shaft is rotating at a predetermined angularvelocity.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of a snowmobileincorporating the invention.

FIG. 2 is a partial plan view of the snowmobile shown in FIG. 1.

FIG. 3 is a side elevation view of a centrifugal clutch according to theinvention in a first mode.

FIG. 4 is a sectional view of a portion of the clutch shown in FIG. 3taken along line 4-4 of FIG. 3.

FIG. 5 is a sectional view of a portion of the clutch shown in FIG. 3taken along line 44 of FIG. 3, showing an alternate embodiment of theclutch centrifugal weight arrangement.

FIG. 6 is a side elevation view of a centrifugal clutch according to theinvention in a second mode.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to the drawings,a preferred embodiment of the invention is shown in connection with asnowmobile, but it is to be understood that it could be utilized inother vehicle applications.

In general, a snowmobile 10 includes a frame 12, a seat 14 for theoperator and a steering handle 16 for manipulating a pair of steeringskis 18 through a shaft 19 and a linkage 20. A traction belt 22 ismounted over a suspension 24 which is mounted in turn to the frame 12.The traction belt is driven by a pair. of drive sprockets 26 mounted ona shaft 28 and each engageable with a rectilinear succession of sprocketholes 30 in the traction belt. The sprocket drive shaft 28 is driven bya motor 32 through a variable speed drive, generally designated 34.

The variable speed drive 34 includes a drive shaft 36 extending from androtated by motor 32. First and second pulley flanges, 38 and 40respectively, are mounted on drive shaft 36 for rotation along therewithand provide therebetween a groove 42 for engaging and driving a V-belt44. First pulley flange 38 is fixed on shaft 36 against axial movement.The second pulley flange 40 is axially shiftable to vary the size ofgroove 42 and thus the radial position of V-belt 44 with respect to thepulley flanges. The pulley flanges 38 and 40 are mounted on shaft 36 sothat at engine idling speed there is a gap between the V-belt and thepulley flanges and the V-belt is not driven thereby.

A driven shaft 46 is mounted in parallel spaced relationship with driveshaft 36. A pair of opposed pulley flanges, 48 and 50 respectively, aremounted on the driven shaft 46 and form a groove 52 therebetween inspaced relationship with groove 42 for receiving V-belt 44 such thatshaft 46 can be driven from shaft 36 by the V-belt 44. The sprocketwheel drive shaft 28 is driven from shaft 46 through a sprocket 54mounted thereon, a sprocket (not shown) mounted in spaced relationshiptherewith on the sprocket wheel drive shaft 28 and a chain 56 mountedover both sprockets.

Pulley flange 50 is axially movable on driven shaft 46 against a springbias (not shown) mounted in a housing 58. The normal position of thepulley flanges 48 and 50, that at engine idling speed, is such that theV-belt is at its radially outward position.

With reference to FIG. 3, a centrifugal clutch 60 is mounted on shaft 36for axially shifting pulley flange 40 in response to variations in theangular velocity of the drive shaft. The centrifugal clutch includes acam ramp 62 affixed to the shaft, spring means 64 mounted in a recess 65in the pulley flange 40 to bias the latter away from pulley flange .38,and a plurality of centrifugal weights 66 mounted for rolling movementbetween said cam ramp and said movable pulley flange. A member 68retains the spring 64 in the recess 65.

A plurality of guide flanges 69 are provided on pulley flange 40 andextend toward cam ramp 62. These flanges serve to maintain thecentrifugal weights rolling in a radial direction.

With reference to FIG. 4, each of the centrifugal weights 66 includes athreaded rod 70, first andsecond wheels 74 and 76 mounted on said rodand separated by a member 78 that is bearingly mounted on the rod 70.Nuts 82 and 84 mounted on the rod outside of wheels 74 and 76 secure thewheels and the member 78 in place on the rod 70.

The centrifugal weights are guided in a radial direction by positioningthem with the wheels 74 and 76 on either side of the flanges 69 formedon the pulley flange 40. With this arrangement, the bearing member 78abuts flange 69 and rolls therealong to reduce friction therebetweenwhile the periphery of the wheels 74 and 76 roll along the surface ofcam ramp 62.

With reference to FIG. an alternate embodiment of a centrifugal weight66' is shown and includes a rod 87 having a single wheel 88 mountedthereon, a bearing 89 mounts the wheel for free rotational movement onrod 87 and the rod for rotational movement with respect to the wheel.The centrifugal weight 66' is mounted with the periphery of wheel 88rolling on the cam ramp and the bearing 89 rolling on the pulley flange.A recess 90 is provided in the pulley flange to free the periphery ofthe wheel from all contact except with the cam ramp.

In operation, with the clutch as described hereinabove, as the operatorof the vehicle depresses the motor throttle control to initiate movementof the vehicle, the motor RPMs increases thereby increasing the angularvelocity of the drive shaft. This causes the centrifugal weights 66 or66' to roll radially outwardly, forcing the pulley flange 40 towardpulley flange 38 against the spring bias between pulley flange 40 andcam ramp 62. Initially, this causes the V-belt to be engaged by bothpulley flanges and to be driven thereby.

With continued increasing motor speed and drive shaft angular velocity,the centrifugalweights continue to roll radially outwardly and the camramp progressively forces pulley flange 40 toward pulley flange 38 andthe V-belt 44 moves radially outwardly in groove 42. This exerts aradially inward pull on the V-belt portion between pulley flanges 48 and50 and the pulley flange 50'is displaced to the right as seen in FIG. 2against the spring means in housing 58 to accommodate the inwardmovement of the V-belt.

In this way, as the operator of the snowmobile increases his throttlepressure, the vehicle will go from a stationary idle to a high torque,low speed acceleration to a high speed, low torque cruise speed. Thebearingly mounted idler-type centrifugal weights enable changes invehicle speed to be made smoothly and with precision.

For racing applications, a notch 92 is provided adjacent the inner endof each of the flanges 69. The notch is sized and located such that whenthe motor is in its idle mode the spring 64 will urge the flange 69 to aposition where the notch will receive therein the bearing member 78 ofthe centrifugal weights of FIG. 4 or the rod 87 of the centrifugalweights of FIG. 5. Thus, when engine RPMs are increased, instead of thecentrifugal weightsrolling between the flanges 69 and the cam ramp 62 togently engage and move the V-belt 44 outwardly as described hereinabove,the spring and notch will retain the centrifugal weights in place untilthe angular velocity of the shaft is increased to a point predeterminedby the strength of spring 64 and the slope of the notch radially outersurface of the notch 92, whereupon the lateral component of thecentrifugal force of the centrifugal weights will overcome the retainingimpulse of the notch and spring and the weights will lurch outwardlyalong the cam ramp and the upper part of flange 89, forcing the pulleyflange 40 suddenly and substantially to the left as seen in FIGS. 3 and6, engaging the V-belt 44 and forcing it outwardly in groove 42.

Thus, the snowmobile will be suddenly driven forward from a stop througha high acceleration to a high speed mode, which is highly desireable atthe start of a race.

To utilize the same clutch for recreational driving, the notch 92 can beby-passed by emplacing a screw 94 in a hole 96 in the cam ramp 62.Thescrew prevents the spring 64 from urging the pulley flange 40sufficiently to the right toallow the notch to receive the bearings 78or rods 87, as seen in FIG. 3. With the screw in position, then, theclutch will operate as if the notches 92 were not there.

The clutch engagement speed can be made adjustable by making the screwposition adjustable and curving the radially outward surface of thenotch 92. With this arrangement, the sensitivity of the clutch toparticular engine speeds can be adjusted by manipulation of the screw.

Having now fully set forth both structure and operation of preferredembodiments of the concept underlying the present invention, it may bethat various other embodiments as well as certain variations and modifications of the embodiments herein shown and described will occur tothose skilled in the art upon becoming familiar with said underlyingconcept. All such embodiments, variations, and modifications asincorporate the spirit of the invention and depend upon its underlyingconcept are consequently to be considered as within the scope of theclaims appended herebelow, unless the claims by their language expresslystate otherwise.

I claim:

1. In a centrifugal clutch having a drive shaft and a pulley flangemounted for slidable movement on said drive shaft to engage said clutch,apparatus for sliding said pulley flange, comprising:

a cam ramp in spaced relationship with said slidable pulley flange,

a centrifugal weight mounted for radial movement between said pulleyflange and said cam ramp, and

means for retaining the centrifugal weight against radial movement belowa predetermined drive shaft angular velocity, and

further comprising means selectively attachable to said clutch forby-passing said centrifugal weight retaining means. I

2. In a centrifugal clutch having a drive shaft and a pulley flangemounted for slidable movement on said drive shaft to engage said clutch,apparatus for sliding said pulley flange, comprising:

a cam ramp in spaced relationship with said slidable pulley flange,

a centrifugal weight mounted for radial movement between said pulleyflange and said cam ramp, and

means for retaining the centrifugal weight against radial movement belowa predetermined drive shaft angular velocity, and

wherein: said means for retaining the centrifugal weight against radialmovement includes a recess formed in said slidable pulley flange andadapted to receive a portion of said centrifugal weight therein andmeans biasing said slidable pulley flange toward said centrifugalweight, and

further comprising means selectively attachable to said clutch forby-passing said recess in the slidable pulley flange by precluding theengagement of said notch with said centrifugal weight.

3. Apparatus according to claim 2, wherein said selective by-passingmeans is adjustable for providing selectable slidable movement of thepulley flange with respect to the cam ramp to vary the speed at whichclutch engagement occurs.

4. In a centrifugal clutch including a drive shaft, a pair of pulleyflanges mounted on said drive shaft and providing therebetween a groovefor a V-belt, one of the pulley flanges being axially movable on thedrive shaft to vary the radial position of the V-belt with respect tothe pulley flanges, apparatus for axially moving said movable pulleyflange in response to the angular velocity of the drive shaft,comprising:

a cam ramp fixedly mounted to said drive shaft in spaced relationshipwith the side of the movable pulley flange away from the other pulleyflange, said cam ramp including a portion curved toward said movablepulley flange,

a centrifugal weight mounted for radial movement with respect to saidmovable pulley flange and said cam ramp, and

means for inhibiting the radial movement of said centrifugal weightuntil a predetermined drive shaft angular velocity is reached, and vwherein said centrifugal weight includes:

a rod,

a pair of wheels mounted on said rod for rolling engagement with saidcam ramp, and

a bearing of smaller diameter than the wheels on said rod between saidwheels for rolling engagement with said pulley flange, and

5. In a centrifugal clutch including a drive shaft, a A

pair of pulley flanges mounted on said drive shah and providingtherebetween a groove for a V-belt, one of 0 the pulley flanges beingaxially movable on the drive shaft to vary the radial position of theV-belt with respect to the pulley flanes, apparatus for axially movingsaid movable pulley flange in response to the angular velocity of thedrive shaft, comprising:

a cam ramp fixedly mounted to said drive shaft'in spaced relationshipwith the side of the movable pulley flange away from the other pulleyflange, said cam ramp including a portion curved toward said movablepulley flange,

a centrifugal weight mounted for radial movement with respect to saidmovable pulley flange and said cam ramp, and

means for inhibiting the radial movement of said centrifugal weightuntil a predetermined drive shaft angular velocity is reached, and

wherein said centrifugal weight includes:

a rod,

a pair of wheels mounted on said rod for rolling engagement with saidcam ramp, and

a bearing of smaller diameter than the wheels on said rod between saidwheels for rolling engagement with said pulley flange, and

wherein a pair of guide members are mounted on the cam ramp, spacedapart a distance sufficient to receive both wheels therebetween.

6. Apparatus according to claim 4, wherein a plurality of guideways aremounted on said pulley flange equidistantly therearound, a rollingweight is mounted on each guideway and a pair of guide members aremounted on the cam ramp to receive both wheels of each rolling weighttherebetween.

7. In a centrifugal clutch including a drive shaft, a pair of pulleyflanges mounted on said drive shaft and providing therebetween a groovefor a V-belt, one of the pulley flanges being axially movable on thedrive shaft to vary the radial position of the V-belt with respect tothe pulley flanges, apparatus for axially moving said movable pulleyflange in response to the angular velocity of the drive shaft,comprising:

a cam ramp fixedly mounted to said drive shaft in spaced relationshipwith the side of the movable pulley flange away from the other pulleyflange, said cam ramp including a portion curved toward said movablepulley flange,

a centrifugal weight mounted for radial movement with respect to saidmovable pulley flange and said cam ramp, and

means for inhibiting the radial movement of said centrifugal weightuntil a predetermined drive shaft angular velocity is reached, and

wherein said centrifugal weight includes:

a rod,

a wheel bearingly mounted on said rod for rotation with respect theretoand rolling engagement with said cam ramp,

a guideway mounted on said pulley flange and extending therefrom towardssaid cam ramp, said guideway having a recess therein to accept a portionof said wheel therein, and

the bearing of said roller weight being mounted for rolling engagementwith said guideway on both sides of said recess.

1. In a centrifugal clutch having a drive shaft and a pulley flange mounted for slidable movement on said drive shaft to engage said clutch, apparatus for sliding said pulley flange, comprising: a cam ramp in spaced relationship with said slidable pulley flange, a centrifugal weight mounted for radial movement between said pulley flange and said cam ramp, and means for retaining the centrifugal weight against radial movement below a predetermined drive shaft angular velocity, and further comprising means selectively attachable to said clutch for by-passing said centrifugal weight retaining means.
 2. In a centrifugal clutch having a drive shaft and a pulley flange mounted for slidable movement on said drive shaft to engage said clutch, apparatus for sliding said pulley flange, comprising: a cam ramp in spaced relationship with said slidable pulley flange, a centrifugal weight mounted for radial movement between said pulley flange and said cam ramp, and means for retaining the centrifugal weight against radial movement below a predetermined drive shaft angular velocity, and wherein: said means for retaining the centrifugal weight against radial movement includes a recess formed in said slidable pulley flange and adapted to receive a portion of said centrifugal weight therein and means biasing said slidable pulley flange toward said centrifugal weight, and further comprising means selectively attachable to said clutch for by-passing said recess in the slidable pulley flange by precludinG the engagement of said notch with said centrifugal weight.
 3. Apparatus according to claim 2, wherein said selective by-passing means is adjustable for providing selectable slidable movement of the pulley flange with respect to the cam ramp to vary the speed at which clutch engagement occurs.
 4. In a centrifugal clutch including a drive shaft, a pair of pulley flanges mounted on said drive shaft and providing therebetween a groove for a V-belt, one of the pulley flanges being axially movable on the drive shaft to vary the radial position of the V-belt with respect to the pulley flanges, apparatus for axially moving said movable pulley flange in response to the angular velocity of the drive shaft, comprising: a cam ramp fixedly mounted to said drive shaft in spaced relationship with the side of the movable pulley flange away from the other pulley flange, said cam ramp including a portion curved toward said movable pulley flange, a centrifugal weight mounted for radial movement with respect to said movable pulley flange and said cam ramp, and means for inhibiting the radial movement of said centrifugal weight until a predetermined drive shaft angular velocity is reached, and wherein said centrifugal weight includes: a rod, a pair of wheels mounted on said rod for rolling engagement with said cam ramp, and a bearing of smaller diameter than the wheels on said rod between said wheels for rolling engagement with said pulley flange, and wherein said pulley flange includes a guideway extending toward the cam ramp outwardly therealong, and said wheels are mounted on the rod in positions spaced laterally away from the sides of the guideway such that the wheels are guided thereby.
 5. In a centrifugal clutch including a drive shaft, a pair of pulley flanges mounted on said drive shaft and providing therebetween a groove for a V-belt, one of the pulley flanges being axially movable on the drive shaft to vary the radial position of the V-belt with respect to the pulley flanes, apparatus for axially moving said movable pulley flange in response to the angular velocity of the drive shaft, comprising: a cam ramp fixedly mounted to said drive shaft in spaced relationship with the side of the movable pulley flange away from the other pulley flange, said cam ramp including a portion curved toward said movable pulley flange, a centrifugal weight mounted for radial movement with respect to said movable pulley flange and said cam ramp, and means for inhibiting the radial movement of said centrifugal weight until a predetermined drive shaft angular velocity is reached, and wherein said centrifugal weight includes: a rod, a pair of wheels mounted on said rod for rolling engagement with said cam ramp, and a bearing of smaller diameter than the wheels on said rod between said wheels for rolling engagement with said pulley flange, and wherein a pair of guide members are mounted on the cam ramp, spaced apart a distance sufficient to receive both wheels therebetween.
 6. Apparatus according to claim 4, wherein a plurality of guideways are mounted on said pulley flange equidistantly therearound, a rolling weight is mounted on each guideway and a pair of guide members are mounted on the cam ramp to receive both wheels of each rolling weight therebetween.
 7. In a centrifugal clutch including a drive shaft, a pair of pulley flanges mounted on said drive shaft and providing therebetween a groove for a V-belt, one of the pulley flanges being axially movable on the drive shaft to vary the radial position of the V-belt with respect to the pulley flanges, apparatus for axially moving said movable pulley flange in response to the angular velocity of the drive shaft, comprising: a cam ramp fixedly mounted to said drive shaft in spaced relationship with the side of the movable pulley flange away from the other pulley flange, said cam ramp including a portion curved toward said movable pulley Flange, a centrifugal weight mounted for radial movement with respect to said movable pulley flange and said cam ramp, and means for inhibiting the radial movement of said centrifugal weight until a predetermined drive shaft angular velocity is reached, and wherein said centrifugal weight includes: a rod, a wheel bearingly mounted on said rod for rotation with respect thereto and rolling engagement with said cam ramp, a guideway mounted on said pulley flange and extending therefrom towards said cam ramp, said guideway having a recess therein to accept a portion of said wheel therein to accept a portion of said wheel therein, and the bearing of said roller weight being mounted for rolling engagement with said guideway on both sides of said recess. 